Development of a model-based transient calibration process for diesel engine electronic control module tables – Part 2: modelling and optimization

This is the second part of a study investigating a model-based transient calibration process for diesel engines. The first part addressed the data requirements and data processing required for empirical transient emission and torque models. The current work focuses on modelling and optimization. The unexpected result of this investigation is that when trained on transient data, simple regression models perform better than more powerful methods such as neural networks or localized regression. This result has been attributed to extrapolation over data that have estimated rather than measured transient air-handling parameters. The challenges of detecting and preventing extrapolation using statistical methods that work well with steady-state data have been explained. The concept of constraining the distribution of statistical leverage relative to the distribution of the starting solution to prevent extrapolation during the optimization process has been proposed and demonstrated. Separate from the issue of extrapolation is preventing the search from being quasi-static. Second-order linear dynamic constraint models have been proposed to prevent the search from returning solutions that are feasible if each point were run at steady state, but which are unrealistic in a transient sense. Dynamic constraint models translate commanded parameters to actually achieved parameters that then feed into the transient emission and torque models. Combined model inaccuracies have been used to adjust the optimized solutions. To frame the optimization problem within reasonable dimensionality, the coefficients of commanded surfaces that approximate engine tables are adjusted during search iterations, each of which involves simulating the entire transient cycle. The resulting strategy, different from the corresponding manual calibration strategy and resulting in lower emissions and efficiency, is intended to improve rather than replace the manual calibration process.

Wom(b)anism: Reading Relationships Between the Community and the Womb in Sankofa, The Women of Brewster Place, and Corregidora

This project attempts to contribute to the various discourses within the black womanist tradition. In 1983, Alice Walker published her landmark collection of essays entitled In Search of Our Mother Gardens: Womanist Prose. At the outset of the volume, Walker defines the core concept of womanism. After a poetic four-part definition of the term womanist, Walker concludes by stating, 'womanist is to feminist as purple to lavender' (Phillips 19). Although this analogy is critically engaged, the scholarly discourse that emerged in response to Walker's proposition shapes the intellectual inner workings of this project. Certain established concepts (such as ancestral mediation or the laying on of hands) work in conjunction with my own concepts of 'wom(b)anism' and 'the communal womb' to frame the interpretive discussions throughout these pages. Wom(b)anism and the communal womb both emerge from the black feminist and womanist traditions, especially via the role of ancestral mediation but also within the contested discourses on womanism itself. I apply the two concepts (wom(b)anism and the communal womb) to my readings of Haile Gerima's Sankofa, Gloria Naylor's The Women of Brewster Place, and Gayl Jones' Corregidora. The relationship between the community and women's wombs across each of these texts construct a narrative that features ancestral mediation (or intervention), various acts of violence committed against women's bodies, and the complicated circumstances through which women heal themselves andtheir communities.